<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
    <style>
      body{
        background: #8374c4;
      }
      .main{
        width: 400px;
        height: 300px;
        background: rgba(37, 30, 30, 0.6);
        position: absolute;
        left: 50%;
        top: 50%;
        transform: translate(-50%,-50%);
        box-shadow: 0px 15px 25px 0 rgba(35, 26, 26, 0.6);

      }
      .main h1{
        color: white;
        text-align: center;
        font-size: 20px;
        margin-top: 15px;
        margin-bottom: 30px;
      }
      .main div{
        width: 80%;
        height: 40px;
        position: relative;
        margin: 0 auto;
        border-bottom: 1px solid white;
        margin-bottom: 40px;
      }
      .main div label{
        font-size: 20px;
        color: rgb(71, 10, 184);
        position: absolute;
        top: 5px;
        left: 0;
        transition: all .2s linear ;
      }
      .main div input{
        width: 100%;
        height: 100%;
        padding-top: 20px;
        box-sizing: border-box;
        border: none;
        background: none ;
        position: absolute;
        bottom: 0;
        left: 0;
        outline: none;
        color: white;
      }
      .btn{
        width: 80px;
        height: 40px;
        margin-left: 40px;
        overflow: hidden;
        color: #fffefe;
        text-transform: uppercase;
        font-size: 10px;
        position: relative;
        background: transparent;
        border: none;
        outline: none;
        cursor: pointer;
      }
      .btn span{
        position: absolute;

      }
      .btn span:nth-child(1){
        width: 100%;
        height: 2px;
        left: -100%;
        top: 0;
        background:-webkit-linear-gradient(left,transparent,#03e9f4);
        animation: login1 .5s linear infinite;
      }
      @keyframes login1{
        100%{
          left: 100%;
        }
      }
      .btn span:nth-child(2){
        width: 2px;
        height: 100%;
        right: 0;
        top: -100%;
        background:-webkit-linear-gradient(top,transparent,#03e9f4);
        animation: login2 .5s .25s linear infinite;
      }
      @keyframes login2{
        100%{
          top: 100%;
        }
      }
      .btn span:nth-child(3){
        width: 100%;
        height: 2px;
        right: -100%;
        bottom: 0;
        background:-webkit-linear-gradient(right,transparent,#03e9f4);
        animation: login3 .5s .5s linear infinite;
      }
      @keyframes login3{
        100%{
          right: 100%;
        }
      }
      .btn span:nth-child(4){
        width: 2px;
        height: 100%;
        left: 0;
        bottom: -100%;
        background:-webkit-linear-gradient(bottom,transparent,#03e9f4);
        animation: login4 .5s .75s linear infinite;
      }
      @keyframes login4{
        100%{
          bottom: 100%;
        }
      }

      .main div input:focus+label,.main div input:valid+label{
        top: 0;
        font-size: 10px;
      }

      .btn:hover{
        box-shadow:inset 0 0 40px rgba(3,233,244,.3),0 0 20px rgba(3,233,244,.3);
      }
    </style>
</head>
<body>
<div class="container">
  <div class="panel panel-success">
    <div class="panel-heading panel-title text-center">
    </div>
    <div class="main">
      <h1>欢迎登录</h1>
      <form action="/users/login" class="form-horizontal" method="post">
        <div>
          <input id="UserName" name="UserName" type="text">
          <label>username</label>

        </div>
        <div>
          <input id="Password" name="Password" type="password">
          <label>password</label>
        </div>

        <button class="btn" type="submit">submit
          <span></span>
          <span></span>
          <span></span>
          <span></span>
        </button>
      </form>
    </div>
  <div class="panel-footer text-right">
    百度在线考试平台
  </div>
</div>
</div>
</body>
</html>
